The 49ers placed Aiyuk (knee) on injured reserve Wednesday.

Coach Kyle Shanahan confirmed Monday that Aiyuk sustained tears to the ACL and MCL in his right knee during Sunday's loss to the Chiefs, Nick Wagoner of ESPN.com reports.

Aiyuk reportedly suffered a torn ACL and MCL during Sunday's loss to the Chiefs, according to Ian Rapoport of NFL Network.

Aiyuk's tests on his injured knee Monday revealed a season-ending injury, Jordan Schultz of Fox Sports reports.

Coach Kyle Shanahan said after Sunday's 28-18 loss to the Chiefs that the 49ers are worried that Aiyuk tore his ACL, Adam Schefter of ESPN reports.

Aiyuk won't return to Sunday's contest against the Chiefs due to a knee injury, Cam Inman of The San Jose Mercury News reports.

Aiyuk went to the locker room on a cart due to an undisclosed injury at halftime of Sunday's game against the Chiefs, Eric Branch of the San Francisco Chronicle reports.

Aiyuk is expected to serve as the 49ers' No. 1 receiver for at least Sunday's game against the Rams after San Francisco head coach Kyle Shanahan said Monday that Deebo Samuel (calf) is likely to miss "a couple weeks," Ron Kroichick of the San Francisco Chronicle reports.

Aiyuk had four receptions (five targets) for 43 yards in Sunday's 23-17 loss to Minnesota.

Head coach Kyle Shanahan said Saturday he'd be "surprised" if Aiyuk saw a full workload in the season opener Monday against the Jets, Eric Branch of the San Francisco Chronicle reports.